It is already known to produce biogas by means of organic materials and particularly garbage obtained from the collection of household refuse by means of an anaerobic digestion eventually aided by an appropriate inoculation. According to one such known process, the garbage provided from the collection is first crushed or pulverized and sorted to remove the heavy portions, such as metals, glass, and the like. The lighter parts, comprising essentially organic materials, are mixed with water, sewage sludges, liquid manure, etc., and/or still another appropriate inoculant, and subjected to anaerobic digestion processes in order to produce biogas from a liquid mass, comprising in general at least 15% dry material.
According to a process described in French Pat. No. 2,327,974, one process for treating household waste is known in which the preliminarily crushed waste is moistened by means of a liquid inoculant during fermentation, and the liquid inoculant is recycled. This known process produces methane, and necessitates a fermentation period of 15 to 30 years. After a time of about 15 years, the refuse is usable as fertilizer, but after 30 years such use is no longer possible.
The present invention has as an object a process of anaerobic composting or anaerobic digestion, at great speed, of solid or solid-like organic material, in which the degradation by anaerobic digestion is almost complete and is accomplished in a matter of several days up to 3 months. Another object of the invention comprises an anaerobic digestion process for nonliquid organic materials in which the undesirable side effect of initial acidification of the organic material is eliminated.
Moreover, the invention makes it possible to obtain a residual product in the form of stabilized, or substantially stabilized compost which is odorless or substantially odorless, not needing further treatment.